This invention relates to mine brattices and more particularly, it concerns improvements in mine brattice structures and in methods for the installation of brattices.
Brattices are commonly used in underground mining as a wall or curtain by which a mine tunnel is sealed against the passage of air or other gases primarily though not exclusively for controlling the flow of air for mine ventillation. In the room and pillar technique commonly employed in the underground mining of coal, for example, brattices are extensively used to seal cross cuts or lateral tunnels to separate air intake and exhaust passages so that ventillating air pumped by fans will be caused to flow from the mine entry to the working faces and back out through the exhaust passages. Brattices are also used to separate working sections of underground mines from previously mined gob areas again to facilitate ventillation of the active or working section but also to prevent the passage of flammable and/or toxic gases from the gob areas to the working section of the mine.
Mine brattices or stoppings are generally classified as permanent or temporary. As these terms imply, temporary brattices are usually in the nature of curtains of canvas, sail cloth or other fabric materials and are employed in the vicinity of the working face of the mine to achieve complete effectiveness of the mine ventillating system, because they are easily and quickly installed and also because they allow passage of men and equipment as needed to facilitate the mining operation. Permanent brattices, on the other hand, are customarily constructed of concrete, cinder blocks or other masonry materials and are accordingly installed rearwardly of the mining operations as the working face is advanced.
While the use of masonry materials is effective to provide a fireproof permanent brattice with adequate wall strength to accommodate the ventillating air pressure differentials which may exist remotely from the mine face to which air must be pumped as well as pressures due to blasting, it will be appreciated that the costs incident to materials, material haulage and labor for installation of masonry brattices are substantial and that the materials cannot be recovered economically for reuse. Moreover, because such brattices do not yield, they are vulnerable to failure as a result of extreme compressive forces brought about by mine roof sagging or floor heaving. Failure under such loading is often manifested by a total collapse of the masonry structure, thereby requiring a substantial reconstruction of the brattice for maintenance of the mine ventillating system.
The problems associated with masonry brattices or stoppings, particularly those resulting from roof or floor squeeze, have been recognized in the prior patent art; for example, U.S. Pat. No. 2,729,064 issued Jan. 3, 1956 to J. R. Kennedy et al and U.S. Pat. No. 3,863,554 issued Feb. 4, 1975 to Newton A. Boyd. In the Kennedy et al patent disclosure, telescopic sheet metal channels extending from the mine floor to the roof are secured in adjacent fashion from transverse supports extending between opposite ribs of the mine tunnel to be closed. Such a structural organization satisfies the requirements of permanent brattices for fireproofing and strength as well as providing a facility for accommodating irregularities in the roof and floor profile. The achievement of a seal along the ribs, however, is difficult because of the linear conformation of the telescopic channel members in contrast to the irregular surface of the ribs. Also the telescopic channel members entail significant fabrication expense. In the Boyd patent, a pliable plastic brattice cloth or laminate is supported on a sealing frame in turn retained against the periphery of the mine tunnel by interconnected extensible jacks having a provision for yielding under conditions of severe roof squeeze. Although brattice cloth may be made to satisfy fireproofing requirements of mine brattices, the strength of such material is less than that required, for example, to withstand pressure differentials developed by blasting. Also, a supporting framework of interdependent jacks or strut-like members is likely to result in a failure in one such member as a result of localized strain deformation of another such member.
Hence it will be appreciated that while mine brattices have evolved to a reasonably refined state of development, there is need for improvement particularly in brattices which fulfill the requirements of permanent stoppings but at lower overall costs to the mine operator than are presently incurred.